1. Field of the Invention
The present invention relates to a semiconductor device which can transmit electrical signals between two circuits whose input electrical signals differ in electrical potential.
2. Description of the Related Art
A photocoupler is often used to transmit electrical signals between two circuits whose input electrical signals differ in electrical potential. The photocoupler has a light emitting element such as a light emitting diode and a light receiving element such as a phototransistor. Thus, the photocoupler converts an inputted electrical signal into light using the light emitting element, reconverts the light into an electrical signal using the light receiving element, and thereby transmits the electrical signal.
However, the photocoupler, which has a light emitting element and light receiving element, is difficult to downsize. Also, the photocoupler cannot follow high-frequency electrical signals. To solve these problems, a technique which transmits an electrical signal by inductively coupling two inductors has been developed, such as described in National Publication of International Patent Application No. 2001-513276.
Also, Japanese Patent Laid-Open No. 2008-283172 and International Publication No. 2004-112138 describe a technique which involves placing a circuit inside an inductor when seen in planar view, where the inductor is used as an antenna.
However, the present inventor has newly noticed the following problem. To downsize elements which transmit electrical signals between two circuits whose input electrical signals differ in electrical potential, it is conceivable to form inductors in interconnect layers using manufacturing technology for semiconductor device and placing the inductors face to face to each other. When two inductors in a semiconductor device are inductively coupled in this way to transmit electrical signals, the installation of the two inductors may increase the size of the semiconductor device.